Presently, when air bag covers are provided in an automobile, the air bag is stored in a steering wheel, in a seat bottom side or seat back side or door panel, or in an instrument panel of the vehicle. During automatic inflation of the driver's side air bag, at least a portion of the air bag cover moves away from the steering column to permit the air bag to perform its safety function between the steering column and the operator of the vehicle.
A recent practice in the automotive industry is utilization of all plastic fabricated air bag covers. Conventional air bag covers used in conjunction with occupant restraint systems often include various connection systems for attaching the air bag cover to the uninflated air bag container.
U.S. Pat. No. 4,325,568 issued to Clark et al. discloses a modular occupant restraint system including an inflator, a cushion, a container for the cushion and an air bag cover for the container assembled as a module. Clark et al. utilizes a two piece air bag cover construction.
U.S. Pat. No. 5,085,462 issued to Gaultier discloses an air bag and vehicle horn switch assembly. Gaultier also discloses a conventional two piece cover construction.
U.S. Pat. No. 5,186,490 issued to Adams et al. discloses a cover for an inflatable restraint system for a motor vehicle which contains a slot in the upper wall thereof into which a replaceable thin or membrane type switch assembly in inserted. Adams et al. further discloses an air bag cover having an injection molded thermoplastic upper wall and a soft outer cover exposed to the interior of the vehicle manufactured from urethane, vinyl or polyester. The outer cover completely encompasses and overlaps the upper wall structure and an uninflated air bag forming two structures the air bag must exit to carry out its function.
The U.S. Pat. No. to Embach, 4,934,735, discloses a device which has inner and outer covers or plates, each of which has split lines which separate the upper walls into upwardly and oppositely opening upper and lower pairs of flaps to permit deployment of the inflatable cushion. A switch assembly is located between either or both pair of flaps and includes one or more membrane switches located between the flaps and respective key pads projecting outwardly of the cover flap for closing respective pairs of circuits on the upper and lower flexible membranes of the membrane switch to each other.
The U.S. Pat. No. to Heidorn, 5,308,106, discloses an air bag module cover assembly with a switch subassembly removably attached at a front surface of the assembly.
The U.S. Pat. No. to Winget, 5,062,661, discloses a rigid plate attached to the substantially rigid remainder of a front panel of an air bag cover to define a hollow compartment which together move upon manual actuation of a flexible, manually operable diaphragm at the front surface of the front panel. Upon separation from the side panel, the front panel, including the diaphragm, the hollow compartment and a rigid plate move together to permit the inflating air bag to leave the cover. The front panel has a first electrically conductive inner surface for making a circuit path with a corresponding second electrically conductive inner surface of the rigid plate.
The U.S. Pat. No. to Cooke, II, 5,344,185, discloses an air bag cover having a replaceable horn switch and a removable cover band.
The U.S. Pat. No. to Leonelli 5,369,232 discloses a membrane horn blow switch integrated into the front panel of an air bag cover. More specifically, the membrane switch seats in and fills a horn actuation area which is a step-down portion of the cover reduced in thickness to approximately 1.0-2.0 mm. The thinning of this "horn actuation area" is said to increase the flexibility of the cover. The horn actuation area is bounded at its vertical extremes by posts which project rearwardly from the inner surface of the cover. The "normal thickness" of the front wall of the cover is on the order of 2.5-3.0 mm. The portion of the cover occupied by the actuation area appears to be substantially less than 50% of the surface area of the front panel of the cover.
There are a number of different ways of attaching air bag cover assemblies to air bag housing assemblies. Examples can be found in the following U.S. Pat. Nos.: 5,198,629; 5,371,333; 5,499,841; and 5,413,376. Typically, permanent fasteners such as rivets permanently secure the air bag cover assembly to the air bag housing assembly. Such permanent fasteners may include certain types of adhesives and may also include such things as one-way screws and other fasteners that, while removable, require special tools not widely available. On the other hand, a removable fastener is typically removably secured and includes such things as bolts, screws, clips, or snap-in mountings.
The U.S. Pat. No. to Lang et al., 5,399,819, discloses the use of posts which extend through a membrane horn switch having a front plate and a rigid back plate.
The U.S. Pat. No. to Bowman et al., 5,642,901, discloses a relatively flexible thermoplastic air bag cover including a front panel wherein switch activating members enhance activation of a membrane-type switch located at a switch location area of the front panel.
One problem with many of the prior art air bag cover assemblies is that they must typically be assembled at the same location that the air bag housing assembly is assembled because such air bag cover assemblies include many sections such as a switch section which must be connected to a vehicle's electrical system. This may not be desirable for any number of reasons including the proliferation of loose parts and sections at the final assembly location.